I am strongly considering building and then of course loading for an ar15 rifle! I understand the differences for the most part in the chamber etc for a 223 vs the 5.56 nato. I do not do factory ammo! I have numerous manuals for loading data and of course use the up to date on the net! My question, is there a good site for load data to duplicate the 5.56 round instead of the more mild 223 round? I hope I have made myself clear! Thanks, Tom